import java.util.Scanner;

/**
 * @author vivi
 * @description
 * @date 2024/4/25
 */
public class demo3 {
    public static void main(String[] args)
    {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt(), m = in.nextInt(), x = in.nextInt(), y =
            in.nextInt();
        long[][] dp = new long[n + 2][m + 2];
        dp[0][1] = 1;
        x += 1; y += 1;
        for(int i = 1; i <= n + 1; i++)
        {
            for(int j = 1; j <= m + 1; j++)
            {
                if(i != x && j != y && Math.abs(i - x) + Math.abs(j - y) == 3
                        || (i == x && j == y))
                {
                    dp[i][j] = 0;
                }
                else
                {
                    dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
                }
            }
        }
        System.out.println(dp[n + 1][m + 1]);
    }
}
